There has been a great interest in the development of nanoliter to picoliter microvials in analytical chemistry. Arrays of vials containing nanoliter to picoliter volumes have been etched in silicon for sample introduction in capillary electrophoresis and mass spectroscopy (Clark and Ewing (1998) Anal. Chem., 70: 1119-1125; Clark et al. (1997) Anal. Chem., 69: 259-263).
Previous approaches, however, have not provided a convenient method of regulating the relative surface area of the electrodes exposed in the vials, have not been convenient for the fabrication of large precisely arranged arrays of such vials, or have not been feasible for the preparation of sub micron structures.